The present invention relates to a device for detecting radiation and, more particularly, to a device associated in an X-ray computed tomography scanner for detecting X-rays.
An X-ray computer tomography scanner (hereinafter referred to as "an X-ray CT scanner") has an X-ray detecting array. The array detects the X-rays generated from an X-ray source and transmitted through a body to be inspected and generates signals. These signals are processed to display a tomographic image. A third-generation X-ray CT scanner has an X-ray detecting array formed by arraying, for example, 512 X-ray detecting devices on a circular arc, and rotating the array around the body to be inspected, together with an X-ray source. A fourth-generation X-ray CT scanner has an X-ray detecting array formed by arranging, for example, 2304 X-ray detecting devices in a circle around a body to be inspected. Only an X-ray source is rotated, and the array is secured to the frame of the scanner. A solid-state device in which a scintillator element for converting X-rays into light rays, and a photo-diode bonded to the scintillator element for detecting the converted light rays has been proposed as an X-ray detecting device associated with such an X-ray detecting array, and has been used in the X-ray CT scanner. In this solid-state X-ray detecting device, light rays are absorbed by a scintillator element in the scintillator element for generating light rays by absorbing or scattering the ray. It is pointed out that some ratio of the light rays do not arrive at a photo-diode thus deteriorating the conversion efficiency. In the fourth generation X-ray CT scanner, the scintillator element and the photo-diode are bonded by an optically transparent bonding material to form an X-ray detecting device. Tens of devices are associated in a detector pack, and the packs are arranged in a circle to form a detecting array. This X-ray detecting device has the drawback that the bonding of the scintillator element to the photo-diode by an adhesive lowers the fabricating efficiency, and the positioning of the scintillator element and the photo-diode is not accurate. Further, the adhesive applied between the scintillator element and the photo-diode is likely to exfoliate due to the ambient temperature changes, and its optical properties vary with time to alter the detecting value.